<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>文本框输入内容转化大写</title>
  </head>
  <body>
    <input type="text" name="" id="" />

    <script>
      document.querySelector('input').addEventListener('keyup', function () {
        this.value = this.value.toUpperCase()
      })
    </script>
  </body>
</html>
